1. Field of the Invention
The present invention relates to a color filter for liquid crystal display (LCD) panels, in particular, a color filter with integrally formed multicolor layer and a method of producing the same.
2. Description of the Prior Art
In general, conventional methods for producing color filters for LCD panels utilize various mechanisms to coat three primary colors (red, green and blue) onto predetermined positions of a substrate, followed by separation, filtration and the addition of adhesive. Examples of such methods includes printing, electro-deposition method, colorant dispersion, dyeing, ink-jet etc. The above-mentioned methods and their disadvantages are further discussed as follows:
(1) Printing method: Three primary colors are sequentially printed onto a substrate using a screen board. However it is difficult to control the positions of colors and the uniformity of the thickness of various colors.
(2) Electro-deposition method: Ground colorants are sequentially electro-deposited to predetermined positions by electrical-ionic dispersing agent. But, patterns of colors are limited due to the thickness of colorant affected by difficulty in controlling the uniformity of current.
(3) Colorant dispersion method: Non-ionic surfactant is used as dispersion agent for high molecular colorant to make a colored photosensitive agent. A substrate coated with the photosensitive agent is then subjected to photolithography to obtain expected colored areas. However, three courses of lithography are required, thereby increasing production costs.
(4) Dyeing method: A substrate coated with a dyeable photosensitive agent is exposed to obtain partitioned areas, followed by localized coloring to obtain expected color areas. However, this method exhibits reliability problems, such as deficiency of chemical resistance, heat resistance and litho-resistance.
(5) Ink-jet method: Shown in FIGS. 1a-1c, where 104 represents a substrate, 103 represents black matrix, 102 represents an ink-absorbing layer, and 101a-101c represent ink in different colors. In FIG. 1a, a substrate 104 is prepared for ink-jetting; and contact of ink with the substrate is shown in FIG. 1b. FIG. 1c illustrates the completion of colored substrate. In this method, a substrate is firstly coated with an ink-absorbing layer, followed by another smooth coating of photoresist agent in thick-film. Next, the substrate is subjected to photolithography to attain partitioned areas, followed by ink-jetting to obtain expected colored areas. In this method, three primary colors (red, green, blue) are printed onto the substrate simultaneously, thus the process time and costs for material are more economical than the colorant dyeing method. However, high molecular material is required as adhesion promoter or dispersion agent, which is mostly deficient in resistance to chemicals, heat and light.
In addition, in the above-mentioned methods, three colors are formed in repeated steps. Hence, gaps easily occur between different colors. Also, the thickness of colors is difficult to control. Consequently, there are problems in product quality.
In order to overcome the above problems, an object of the invention is to provide a color filter for LCD panels, in which the multicolor layer of the color filter is formed directly from the oxidization of a metal layer on the substrate, without high molecular material, such as dispersion agent, adhesion agent, and color-absorbing layer. As a result, deficiency in resistance to chemicals, heat and light is avoided.
It is another object of the invention to provide a color filter with high rate of windows, good reliability, and high resolution.
Another object of the invention is to provide a method to produce a color filter that causes less pollution and is low in production costs.
In order to achieve the above objects, there is provided a color filter for LCD panels, comprising a transparent substrate; and a metal layer formed on the substrate, wherein the metal layer contains integrally formed first color layer, second colour layer and third color layer.
Based on this invention, a method for producing a color filter with integrally formed multicolor layer is carried out by repeatedly exposing a transparent substrate coated with a metal layer with the aid of a photoresist layer to form different colors in the metal layer. The pattern of the photoresist layer is predetermined so that the different color layers are formed in the required positions. In the case where black matrix is necessary, it can be easily attained by further exposing the metal layer with another photoresist layer having the pattern of black matrix.